Electrographic recording system with interleaved electrode groups

ABSTRACT

Recording electrodes of a coincidence voltage type electrographic recorder are divided into arrays. Arrays are divided into two or more groups and are interleaved so that no array is adjacent another array of the same group. Like-numbered electrodes of each array in a group are connected together. Complementary electrodes are disposed adjacent to the arrays. Each is adjacent to only one array of a group and is spaced from all other arrays of the same group. A latent image is formed at one selected recording electrode when suitable voltage is applied to that electrode, and in coincidence therewith, suitable voltage is applied to complementary electrode means adjacent to the selected recording electrode.

United States Patent Brown, Jr.

[54] ELECTROGRAPHIC RECORDING SYSTEM WITH INTERLEAVED ELECTRODE GROUPS[72] Inventor: Arling Dix Brown, Jr., Cleveland Heights,

Ohio

[73] Assignee: Clevite Corporation [22] Filed: Oct. 22, 1969 [21]Appl.No.: 868,394

[4 1 Mar. 28, 1972 Primary Examiner-Howard W. Britton Attorney-Eber J.Hyde [57] ABSTRACT Recording electrodes of a coincidence voltage typeelectrographic recorder are divided into arrays. Arrays are divided intotwo or more groups and are interleaved so that no array is adjacentanother array of the same group. Like-numbered electrodes of each arrayin a group are connected together. Complementary electrodes are disposedadjacent to the arrays. Each is adjacent to only one array of a groupand is spaced from all other arrays of the same group. A latent image isformed at one selected recording electrode when suitable voltage isapplied to that electrode, and in coincidence therewith, suitablevoltage is applied to complementary electrode means adjacent to theselected recording electrode.

11 Claims, 10 Drawing Figures will P'ATfiNTEnnms 1912 SHEET 1 []F 5FIG.4

INVENTOR. ARLING DIX BROWN,JR. 2%

ATTORNEY PATENTED MR 2 8 I972 8'. 6 53 O6 5 SHEET 3 [1F 5 I INVENTOR.

ARLING DIX BROWN,JR.

ATTORNEY PATENTEDMmeIQn 3,653,065

sum 5 OF 5 HORIZONTAL SYNC 2| CLOCK 25 COUNTER I23 25 an SHIFT REGISTERINPUT 25 GATES 25 BIT STORAGE GATED GATED I35 LECTRODE DRIVER ELECTRODEDRIVERS SHIFT REGISTER FIG.6

INVENTOR. ARLING DIX BROWN,JR.

TTORNEY ELECTROGRAPI'IIC RECORDING SYSTEM WITH INTERLEAVED ELECTRODEGROUPS BACKGROUND OF INVENTION 1. Field of Invention This inventionrelates to electrographic recording systems. The electrographicrecording process is generally characterized by two basic steps. Thefirst step is the establishment of an electrostatic latent image byelectrically charging areas on selected portions of a record medium byelectrostatic recording electrodes connected to charging circuit means.In the second step the electrostatic latent image is rendered visible bythe toning or developing ofthe charged areas on the record medium. i

The present invention is directed to an improvement in the first step,that is, an improved electrographic imaging system for the establishmentof the electrically charged areas on the record medium.

2. Description of the Prior Art y In general, the prior art providesrecording electrodes which terminate adjacent to the charge retentivesurface of a dielectric layer of the record medium upon which it isdesired to deposit an electrostatic charge. A complementary electrode islocated opposite the side of the record medium on which theelectrostatic charge is to be deposited. For example, in US. Pat. No.-2,919,171 issued Dec. 29, 1959, to Epstein and Phelps, the record mediumis threaded between the recording electrodes and the complementaryelectrode or backing bar and is held in intimate contact with the latterwhile remaining spaced from the former. The signal information voltageof given polarity isapplied to selected recording electrodes, and it isnot great enough, by .itself, to charge an area of the record trodes andemploying capacitive coupling from the complementary electrodes to aconductive layer in the record medium, as more fully described in theabove-mentioned application, Ser. No. 812,821, John Blumenthal. Thisimprovement alone has attendant difficulties however. The voltageinduced at the conductive layer tends to be greatest near the centralregion of the complementary electrode and falls off in areas near theends of the complementary electrode. Thus, recording at electrodes nearthe ends of the complementary electrodes An object of the invention isto provide an improved electrographic recording system whereincapacitive coupling is utilized.

Another object of the present invention is to provide an electrographicrecording system having recording electrode means which are located onlyon one side of the record medium, thereby providing easier threading ofthe record medium.

A further object of the present invention is to provide anelectrographic recording system that, because of capacitive coupling, isessentially insensitive to the thickness and variations in thickness ofthe record medium.

A further object of the present invention is to provide anelectrographic recording system in which critical alignment betweenrecording electrodes and backing electrodes is not required. 7

Further objects and advantages of the invention will appear from thefollowing detailed description to be read in conjunction with theaccompanying drawings wherein like .reference symbols denotecorresponding parts throughout the several figures.

medium. A supplemental voltage of opposite polarity and of a magnitudeinsufficient by itself to cause charging of the record medium is appliedto the complementary electrode which is in physical contact with therecordimedium. When the two voltages are simultaneously applied, theresultant total voltage is sufficient to cause an electrical charge tobe applied from the recording electrode across the air gap to thesurface of the dielectric layer. This is sometimes referred to thecoincident voltage type of electrographic recording.

To reduce the number of driver circuits for applying the requiredcharging voltage to the recording electrodes, the

electrodes may be equally divided into arrays, and likenum- I beredelectrodes in each array may be connected together, providing only asmany recording circuits as there are recording electrodes in a singlearray. A plurality of complementary electrodes or backing bars areprovided, one in registration with each array of recording electrodes.

To form a latent image on the record medium adjacent to one recordingelectrode, the signal information voltage is applied to the circuitconnected to that recording electrode. Due to the interconnections, alllike-numbered recording electrodes receive the same signal informationvoltage.

The supplemental voltage required to establish the latent 7 image isapplied only to the complementary electrode in registration with thearray containing the recording electrode where the image is desired. Thelike-numbered recording electrodes in other arrays are not expected toestablish a latent image because the complementary electrodes associatedwith these arrays are not energized.

One difficulty with prior art recorders is the necessity for threadingthe record medium between the recording electrodes and the complementaryelectrodes. This difficulty has been overcome by placing thecomplementary electrodes on the same side of the record medium as therecording elec- SUMMARY OF THE INVENTION In accordance with thisinvention there is provided an im proved electrostatic recording systemfor'printing on an electric charge retentive record .medium.'Recordingelectrodes are mounted with an area of each electrode in close proximityto the record medium. The recording electrodes are divided into arrays.Circuit means interconnect like-numbered recording electrodes ofseparated arrays to establish at least two electrically independentgroups of arrays, with each array of each group separated from everyother array of that group by at least one array of another group.

Complementary electrode means are mounted with an area of each inelectrical cooperative relationship with the record medium. Eachcomplementary electrode means is mounted adjacent a single array of agroup of arrays and spaced from all other arrays of that group by atleast a portion of an array of another group.

Means are provided for applying a voltage of one polarity to a selectedrecording electrode facing the area on the record medium where it isdesired to establish a latent image. Due to the above-mentioned circuitsinterconnecting recording electrodes in different arrays, the voltagealso is applied to other electrodes where images are not desired.

Means are also provided for applying in coincidence with application ofvoltage to the selected recording electrode, a voltage of oppositepolarity to a complementary electrode means which is adjacent to theselected recording electrode,

'while complementary electrode means adjacent to the other energizedrecording electrodes are maintained in deenergized state. A latent imageis establishedonly where there are coincident voltages on recording andadjacent complementary electrode means.

BRIEF DESCRIPTION OF THE DRAWINGS single-row aligned head.

FIG. 2 is a diagrammatic representation of an electrographic recordingsystem utilizing a recording head similar to the head shown in FIG. 1.

FIG. 3a is a sectional view through lines A-A of FIG. 2.

FIG. 3b is a graph illustrating the action of the electrodes in FIG. 3a.

FIG. 30 is a sectional view through line C-C of FIG. 2.

FIG. 3d is a graph illustrating the action of the electrodes in FIG. 30.

. FIG. 4 is a diagrammatic representation of an electrographic recordingsystem having a different electrode arrangement.

FIG. 4a illustrates a modification of the electrode arrangement ofFIG.4.

FIG. 5 is a diagrammatic representation of an electrographic recordingsystem adapted for a single-line character printing.

FIG. 6 is a diagrammatic representation of an electrographic recordingsystem for making a record of a cathode ray tube display.

DESCRIPTION OF THE PREFERRED EMBODIMENTS use with the present invention.It is described and claimed in the aforementioned US. Pat.applicationnSer. No. 812,821. The head 12 is shown with anelectrographic record medium 14 which is given relative displacement tothe recording means 12 by means not shown. I

The electrographic record medium 14 comprises a dielectric layer orstratum 16 in contact with a conductive portion 18. Suitable thicknessesfor the dielectric layer range from 0.1 to 1.25 mil. Good results havebeen obtained with conductive portions having sheet resistances rangingfrom 0.25 to 1.0 megohm/square. The dielectric layer 16 has an exposedcharge retentive surface 17 which, in operation, substantially engagesthe surface of the head 12. The conductive portion or layer 18 may takea variety of forms. For example, it may be a single layer of conductivematerial, or a plurality of layers of equal or different thicknesses anddifferent conductivities.

The head 12 comprises closely spaced recording electrodes 20 havingrelatively small-area exposed portionsor ends 21, and complementaryelectrodes 22 having relatively large-area exposed portions 23.

The recording electrodes 20 are generally small, closely spaced,electrical conductors embedded in a support 24 composed of a suitabledielectric material such as a plastic or a ceramic, with their end faces21 substantially'flush with the end surface of support 24. By way ofillustration, the recording electrodes 20 can be approximately mils indiameter and spaced on approximately 12.5 mil centers so that they areseparated by about 2.5 mils. The recording electrodes shown in FIG. 1are arranged in a single row; however, they are adapted to a variety ofother arrangements and may, for example, be arranged to representalpha-numeric symbols or the like.

To provide the small, effective gap required for satisfactory recording,the exposed end areas 21 of recording electrodes I 20 may be recessed sothat they are spaced slightly from the record medium. Effective spacingin the range of 0.05 mil to 0.4 mil is desirable. I prefer, however, tohave the end areas flush with the end surface of support 24, and obtainefi'ective spacing by utilizing the invention of US. Pat. applicationSer.

No. 694,654, filed Dec. 29, 1967, in the names of Arling Dix Brown, Jr.,and John Blumenthal, and assigned to the same assignee as the presentinvention. In the Brown and Blumenthal application, small spacingparticles are attached to or embedded in the dielectric layer of therecord medium to provide the desired spacing.

The complementary electrodes 22 are mounted on the support 24 so thattheir surfaces 23 are substantially flush with the end surface of thesupport 24 and the end'faces 21 of the nected.

, 1 4 recording electrodes 20, forming a smooth, preferably slightlycurved surface which the record medium engages during operation of thesystem. The complementary electrodes 22 are generally rectangularlyshaped electrical conductors having their long sides in a parallelrelationship to each other, and having the recording electrodes 20centered between and in a line parallel to the complementary electrodes22.

The recording electrodes 20 extend down into the support 24 and by meansof conductors 26 are connected to energizing circuit means. Conductors30 are connected internally to the complementary electrodes 22 andextend through the support 24 for connections to other energizingcircuit means.

FIG. 2 shows how the recording electrodes and complementary electrodesof a recording head, similar to the head of FIG. 1, may be connected.

The recording electrodes are divided into arrays 31, 32, 33, 34, 35, 36.Each array contains'recording electrodes 1, 2, 3, 4. Like-numberedrecording electrodes of arrays'31, 33, 35 are connected together byconductors 41, 42, 43, 44 to form a first group of arrays 26.Like-numbered recording electrodes of arrays 32, 34, 36 are connectedtogether by conductors 51, 52, 53, 54 to form a second group'of arrays28 which is electrically independent of group 26. Each array in group 26is separated from every other array in group 26 by an array of group 28.

Pairs of complementary electrodes 55, 56, 57, 58, 59, 60, 61 straddlethe row of arrays 31-36. To avoid confusion with the many linesrepresenting interconnections between electrodes 1, 2, 3, 4, not all ofthe complementary electrodes are shown.

The complementary electrode pairs are offset with respect to the arraysso that each array is adjacent to the central area of two complementaryelectrode pairs.

Each complementary electrode pair is adjacent to only one array of onegroup 26 or 28 and is separated from every other array of that group byat least a part of an array of the other group. For example,complementary electrode pair 57 is adjacent to array 33 of group 26. Itis separated from array 31 of group 26 by electrodes 1, 2 of array 32.of group 28. It is separated from array 35 of group 26 by array 34 ofgroup 28.

Recording electrodes nected by conductors 41-44 and 51-54 to means forapplying a voltage of one polarity to selected electrodes. Complementaryelectrodes 55-61 are connected by conductors 63-69 to means for applyinga voltage of opposite polarity to selected electrodes.

For simplicity in illustrating the invention, the selective voltageapplying means are'shown as batteries connected to the electrodes bysimple switches. In the off position, each selector switch grounds 'theelectrodes to which it is con- Battery 38 supplies voltage for therecording electrodes. Electrodes in group 26 are selected by switches71-74, and switch 89. Electrodes in group 28 are selected by switches81-84', and switch 89.

Complementary electrodes 55-61 are selected by switches 75-80. With oneor more of these switches is on, a pulse may be applied by battery 39 tothe selected electrodes by momentarily closing switch 40.

The voltage applied to a selected recording electrode by battery 38alone is insufficient to form a latent image on the record medium.However, when a complementary electrode pair adjacent the selectedelectrode is pulsed by battery 39 through switch 40, the voltage betweenthe selected recording electrode and the conductive layer of the recordmedium is increased momentarily to form the desired latent image. Theincrease in voltage is due to the capacitive coupling between theenergized complementary electrodes and an area of the conductive layerunder the energized recording electrode, as more fully explained incopending application Ser. No. 812,821.

Switch 89 insures that voltage from battery 38 is applied to electrodesof only one group, 26 or 28, at a time. This arrange- 1-4 of groups 26and 28 are conment permits the switches of the unenergized group to beset during the time that recording is taking place at electrodes of theother group.

FIG. 3c is a section taken along line C-C of FIG. 2 showingcomplementary electrode pair 58 and recording electrode 4 adjacent todielectric layer 16 of record medium 14. FIG. 3d is a graph withabscissa corresponding to horizontal position in FIG. 30. The ordinaterepresents the potential of the conductive layer 18 when electrode pair58 are pulsed. The portions of the curve labeled 70a show that as theleft-hand complementary electrode 58 is pulsed alone, the potential ofthe conductive layer peaks under the center of the electrode and fallsoff toward the edges of the electrode. Similarly, the portions of thecurve labeled 70b show the potential distribution for the right-handelectrode 58. The solid line curve shows the potential distribution forthe pair of electrodes 58 when they are connected together as in FIG. 2.The two individual potential distributions 70a and 70b reinforce eachother under recording electrode 4 to establish adequate potential forsatisfactory recording at electrode 4 if it is energized.

FIG. 3a is a section taken along lines A-A of FIG. 2 showingcomplementary electrodes 57, 58, and portions of complementaryelectrodes 56 and 59 adjacent to the dielectric layer 16 of recordmedium 14. FIG. 3b is a graph with abscissa corresponding to thehorizontal position in FIG. 3a. It illustrates how the potential ofconducting layer 18 may vary with position when selected complementaryelectrodes are pulsed. when complementary electrode 58 is pulsed, thepotential of conducting layer 18 is maximum under the center of theelectrode and falls off substantially at the ends of the electrodes.This is illustrated in FIG. 3b by the portions of the curve labeled 62a.Under this condition, satisfactory recording could be made at electrode4, array 33, or at electrode 1, array 34, if either of these electrodeswere energized. On the other hand, at electrode 3, array 33, andelectrode 2, array 34, the pulsed potential of the conductive layer 18could be too low for satisfactory recording. For this reason, I preferto offset the complementary electrodes with respect to the arrays ofrecording electrodes, as shown in FIGS. 2 and 3a, and energize the twopairs of complementary electrodes adjacent to the array at whichrecording is desired. For example, complementary electrode pairs 57, 58are energized together when recording at array 33. The solid line curveof FIG. 3b shows that the potential distribution under array 33, beingthe composite of curves 62a and 62b, is substantially uniform. The twoenergized complementary electrode pairs act as one long complementaryelectrode means extending beyond the selected array of recordingelectrodes so that all of the latter are opposite the region ofconductive layer 18 which is at high potential. The double lengthcomplementary electrode means is made possible by dividing the recordingelectrode arrays into two electrically independent groups.

In F IG. 2, I have shown switch positions for establishing a latentimage only at recording electrode 2, array 33. Switch 89 connectsbattery 38 to switches 71, 72, 73, 74, and grounds switches 81, 82, 83,84. Switch 72 is on, thus energizing electrode 2 of array 33. Due to theinterconnections provided by conductor 42, electrodes 2 of arrays 31 and35 also are energized. Switches 77, 78 are on, thus establishingcomplementary electrode pairs 57, 58 as the complementary electrodemeans for selectively establishing a latent image only at electrode 2,array 33, when pulse switch 40 is actuated. For easy identification, theelectrodes associated with on switches have been shaded or blackened.

Latent images are not established at recording electrodes 2 of arrays31, 35, even though these electrodes are energized because adjacentcomplementary electrodes 55., 56, 59, 60 are grounded. Latent images arenot established at any electrodes of arrays 32, 34, even though some ofthem are close to pulsed complementary electrodes 57, 58 because theyare in a different group and are grounded.

Each complementary electrode 56-60 may be used alternatively as a partof two different complementary electrode means. In the exampleillustrated by switch positions and electrode shading in FIG. 2,electrode 58 is connected to electrode 57 to form complementaryelectrode means for recording electrodes in array 33. However, when alatent image is to be formed at one or more recording electrodes ofarray 34, the same electrode 58 is combined with electrode 59 to formcomplementary electrode means for array 34.

Although I prefer to establish complementary electrode means byenergizing two complementary electrode pairs, it should be understoodthat this is not always necessary. Satisfactory recording may be made atrecording electrodes near the centerline of an energized complementaryelectrode pair without energizing an adjacent complementary electrode.

It should be understood that selected individual recording electrodesmay be energized one at a time, together with adjacent complementaryelectrode means in each case, to record a row of dots in selectedpositions. The record medium may then be advanced and another row ofdots recorded in selected positions, etc., to form a desired compositeimage. The record medium may be stopped for each line recorded, or, itmay be in continuous motion.

Alternatively, depending on the nature of the recording information,several recording electrodes in one array may be energizedsimultaneously.

In the present embodiment there are two rows of flanking complementaryelectrodes. The system of the present invention will also work by usinga single row of complementary electrodes, but usually will requirehigher pulse voltages for the complementary electrodes to offset thefall-off of potential illustrated in FIG. 3d.

The utility of this invention is not limited to systems employingcapacitive coupling of the complementary electrodes to a conductivelayer of the record medium. As an alternative, the electricalcooperative relationship between complementary electrodes and recordmedium may be established by mounting the complementary electrodes tomake electrical contact with the conductive layer as showndiagrammatically in FIG. 4. In FIG. 4 the complementary electrodes arein the form of spring fingers 104, 104'-108, 108 disposed in a rowgenerally opposite the end faces or recording electrodes 1, 2, 3, 4.Precise alignment is not required. The record medium 14 is threadedbetween the end faces of the recording electrodes 1, 2, 3, 4 and thecomplementary electrodes 104-108, with conductive layer 18 in electricalcontact with the complementary electrodes. The recording electrodes arespaced very slightly from the dielectric layer 16 of the record medium.For this purpose the medium preferably is constructed with spacers asdescribed in copending application Ser. No. 694,654.

Recording electrodes 1, 2, 3, 4 are connected to battery 38 throughselector switches 71-74 and 81-84. Complementary electrodes areconnected in pairs 104, 104; 105, 105'; etc., to battery 39 throughselector switches 85-88.

When it is desired to record a dot at a selected electrode, such aselectrode 2 of array 33, for example, switch 72 is closed, applying thevoltage of battery 38 to electrodes 2 of both arrays 31 and 33, but notto arrays 32 or 34. Coincidentally, switches 87 and 88 are closed,applying voltage of opposite polarity from battery 39 to complementaryelectrode means 106, 106, 107, 107. Due to the electrical contactbetween these electrodes and the conductive portion 18, the voltage ofthat part of the conductive portion in the vicinity of chargingelectrode 2, array 33, approaches the voltage of battery 39. Thecombination of the two voltages is sufficient to form a latent image atelectrode 2, array 33.

No image is established at electrodes 2, array 31, because complementaryelectrodes 104, 104', 105, 105' are not energized. Electrodes of array32, which are very close to ener gized complementary electrode 106' donot record because they are in a different group of arrays, andtherefore they are not energized.

As another alternative, the etc. of FIG. 4 may be 105"; etc. as shown inFIG. 4a. 14' need not have a conductive spring fingers 104, 104; 105,replaced by electrodes 104"; In this case the record medium portion.

FIG. shows one way of applying the invention to an electrographiccharacter line printer.

Array 181 contains I05 recording electrodes 201-305 arranged in three 5X7 matrices 191, 192, 193.

Array 182 has recording electrodes similarly arranged in three matrices194, 195, 196.

Array 183 is made up of matrices 197, 198, 199.

Arrays 181, 182, 183 are disposed in horizontal alignment withadditional, identical arrays not shown.

Conductors 93, 105 in number, connect recording electrodes 201-305 ofarray 181 to like-numbered electrodes of the fourth seventh, etc.,arrays, not shown, to establish a first group of recording electrodes.Conductors 93 also connect the first group to switching means 94.

Conductors 96, 105 in number, connectrecording electrodes 201305 ofarray 182 to like-numbered electrodes of the fifth, eighth, etc.,arrays, not shown, to establish a second group of recording electrodes.Conductors 96 also connect the second group to switching means 97.

Conductors 99 interconnect like-numbered recording electrodes of array183 and the sixth, ninth, etc., arrays, not shown, to establish a thirdgroup of recording electrodes. Conductors 99 also connect the thirdgroup to switching means 100.

Adjacent to each array 181, 182, 183, etc., and in alignment therewith,is a pair of complementary electrodes 311, 312, 313, etc. An additionalpair 310 extends beyond the adjacent array 181 and is connected to pair311. A similar pair of complementaryelectrodes, not shown, extendsbeyond the last array on the right hand side.

The recording electrodes 201-305 of each array, and

- aligned complementary electrode pairs 311, 312, 313, etc.,

may be mounted generally as in FIG. 1, but with seven rows of recordingelectrodes, so that the charge retentive coating of the record medium isin close proximity to the exposed areas of all electrodes.

Each switching means 94, 97, 100 is adapted to connect battery 38 toselected recording electrodes 201-305 of the first, second, and thirdgroups, respectively, of electrodes.

Switches 321, 322, 323, etc., connect complementary electrode pairs 311,312, 313, etc., to battery 39 through pulse switch 40.

Latent images of a line of characters may be formed on the record mediumin groups of three. For the-first three characters, appropriate switchesin switching means 94 are turned on, thus energizing those recordingelectrodes 201-305 in array 181 required to form the characters. F orexample, if the first character is to be the letter E then theelectrodes that would be energized are:

Top row20l, 202, 203, 204, 205

2nd row-206 3rd row211 4th row-216, 217, 218, 219, 220

5th row-221 6th row-226 7th row-231, 232, 233, 234, 235 The voltagesapplied to these electrodes is not sufficient to cause a latent image tobe formed at any of the electrodes. Similar electrodes in the fourth,seventh, tenth, etc., arrays also are energized because of theinterconnections provided by conductors 93.

Next, complementary electrode pairs 310, 311 and 312 are energized byclosing switches 321 and 322, and then momentarily closing pulse switch40. The voltage applied to these complementary electrodes momentarilychanges, by capacitive coupling, the voltage of the conductive portionof the record medium under the complementary electrodes and extendingunder the first array 181 so that the voltage difference between thispart of the conductive portion of the record medium and the energizedrecording electrodes in the first array is sufficient to form a latentimage on the medium. Due to the separation of other energized arraysfrom the complementary electrodes which have been energized, there isnot sufficient voltage difference to cause recording at these arrays,even though some of them have electrodes energized in parallel with therecording electrodes of the first array.

Three new characters may be recorded at the second array 182 by closingsuitable switches in switching means 97 to define the characters andenergizing complementary electrode pairs 311, 312, 313 by closingswitches 321, 322, 323, and momentarily closing pulse switch 40.

Three characters may be recorded at the third array 183 by closingsuitable switches in switching means 100 to define the characters, andenergizing complementary electrode pairs 312, 313, 314 by closingswitches 322, 323, 324, and momentarily closing pulse switch 40.

In similar manner, desired characters may be formed in groups of threeat the fourth, fifth, etc., arrays. After a full line has been recorded,the record medium may be advanced and the next line may be recorded.

In the embodiment illustrated in FIG. 5 there are three I groups ofarrays of recording electrodes, with each array of each group separatedfrom every other array of that group by two arrays, one in each of theother groups. At the moment of recording at a selected arraysubstantially uniform complementary potential is established at theconductive layer of the record medium opposite all recording electrodesof the selected array by energizing the complementary electrode pairswhich are in alignment with the selected array and also thecomplementary electrode pairs on either side thereof. With thisthree-group arrangement, oflset between arrays of recording electrodes,and complementary electrodes is not employed. The use of three pairs ofcomplementary electrodes provides, in effect, one long complementarypair approximately three times the length of an array.

FIG. 6 shows an example of how an'electrographic recorder employing thepresent invention may be used. In this example the information to beprinted is taken from a cathode ray tube (CRT) system designed for theexhibit of information in alpha-numeric form. The information to bedisplayed may be fed into the display systems by. an operatormanipulating a typewriter-like keyboard, or the information may comeelectrically from some other source such as a computer, ora'teletypewriter circuit. The beam of the CRT sweeps the screensubstantially as in a conventional television receiver. Electroniccharacter generators selected by the input information supplypulses withappropriate timing to intensity modulate the beam to form the display ofthe selected characters in the selected-sequence and positions. V

The electrical information available for the CRT display system may betapped ofi to actuate an electrographic recorder employing the presentinvention, to obtain a permanent record of the CRT message. Theinformation available from the CRT system is as follows:

1. A clock signal. This is a train of pulses to which all otherinformation is synchronized. The repetition rate may be on the order of8 mI-Iz.

2. Horizontal synchronizing pulses which occur after each CRT horizontalsweep. For convenience, the sweep rate usually is the same as the rateused in US. television broadcasting so that ordinary TV sets or TVmonitors may be used for remote display.

3. Serial binary information which modulates the intensity of the CRTbeam to form the character images one dot at a time.

In the recorder of this example, the recording head 119 is constructedas in FIG. 1. It contains recording electrodes, 600 in a row, dividedinto 24 end-to-end linear arrays, with 25 electrodes in each array.Like-numbered electrodes in the first, third, fifth, etc., arrays areconnected together to form one group of arrays of electrodes andlike-numbered electrodes in the second, fourth, sixth, etc., arrays areconnected together to form a second group of arrays of electrodes.

For the twenty-four arrays there are 25 pairs of complementaryelectrodes 143, 144, 145, To avoid confusion with the many linesrepresenting interconnections between electrodes 120, only onecomplementary electrode of each pair is shown.

The record medium may be advanced over the head 119 at constant speed bya motor-drive mechanism not shown. The speed must be selected tocorrespond to the vertical deflection rate of the CRT display. As willbe discussed in more detail in a later paragraph, this could requiredrive power much greater and more expensive than the applicationwarrants. A simple modification of the CRT system, to be described in alater paragraph, takes care of this situation.

At the beginning of each CRT sweep, a horizontal synchronizing pulse issupplied to line 121. This resets shift registers 168 and storage unit128, resets divide-by-25 counter 130, and resets flip flop 137.

The serial information bits frornthe CRT system are fed via line 123 to25 bit shift register 124. Clock pulses from line 122 advance the bitsfrom right to left through the register.

At every 25th clock pulse, the divide-by-25 counter 130 produces a pulseon line 131. Each pulse at 131 actuates gates 126 to deliver the 25 bitsavailable at output lines 125 from register 124, to 25 bit storage unit128 and to the inputs of gated electrode drivers 135, 136.

The first pulse at 131, after the system has been cleared by thehorizontal synchronizing pulse at 121, triggers flip flop 137 to turn ongated drivers 135. This action is delayed slightly by time delay unit172. Thus, the first 25 bits stored in unit 128 also appear suitablyamplified by drivers 135 at corresponding recording electrodes in allarrays of group 141. The voltages applied to electrodes where recordingis required are not high enough, alone, to establish latent images.

The first pulse at 131, delayed at 172, actuates shift register 168 topresent, at first output 175, the DC level which is connected to input169. This sends pulses through diodes 160, 161 to pulse drivers 153,154. The pulses outputs of 153, 154 are applied to complementaryelectrodes 143, 144 which are adjacent to the first array 148 ofrecording electrodes which is in energized group 141. At this pulseoccurrence latent images are established at the energized electrodes ofarray 148 due to the momentary increase in voltage between thoserecording electrodes and the conductive layer of the record medium inthe regions adjacent to array 148, as described in reference to FIG. 2.The complementary electrodes adjacent to other arrays in group 141(which also have energized electrodes) are not pulsed and, accordingly,no latent images are formed at those arrays.

After the pulsing of complementary electrode means 143, 144, the storageunit 128 is cleared by the first pulse at 131, delayed by delay unit133.

At the 50th pulse, a second pulse occurs at 131. This gates the 26th to50th bits, which now are in shift register 124, to storage unit 128, andthe inputs of gated drivers 135, 136. The pulse at 13], delayed at 172,also triggers flip flop 137 to turn on drivers 136. Consequently, bits26 to 50 appear as high voltages at appropriate recording electrodes inarrays of group 142.

The pulse at 131, delayed at 172, advances the DC level at 169 to output176 of register 168. This sends pulses through diodes 162, 163 todrivers 154, 155 which energize complementary electrode means 144, 145adjacent to the second array 149 and latent images are established atthis array. Next, the storage unit 128 is cleared by the second pulse at131, delayed at 133.

At the 75th clock pulse a third pulse appears at 131 and bits l to 75are applied to recording electrodes of group 141, as in the case of bits1 to 25. Complementary electrode means 145, 146 are pulsed and latentimages are established at array 150.

The above-described process repeats, with appropriate latent imagesbeing established at successive arrays, alternately in group 141 and ingroup 142, until the end of the CRT sweep. A new horizontalsynchronizing pulse then clears and resets the system and recording of anew line begins.

The vertical scan rate in CRT equipment of the kind considered is thesame as the scan rate for conventional U.S. television transmissionwhich is 60 scans per second. This means that the record medium wouldhave to be moved a distance of, say 5 inches in one-sixtieth of asecond. This is a transport rate of 25 feet per. second, which wouldrequire expensive and bulky transport equipment. Furthermore, such largeequipment would require excessive time to reach operating speed and toslow down to a stop, and this would waste large amounts of the recordmedium. Much slower printing of the CRT display information, on theorder of A to 2 seconds, is quite acceptable. This obivates the problemsdiscussed above. I have found that this slower recording may beaccomplished merely by substituting a lower frequency clock in the CRTsystem, 500 kHz. being a suitable frequency. The low frequency clock maybe substituted automatically when the recorder is energized. Theresulting momentary loss of CRT display generally is not considered tobe objectionable.

While there have been described what are at present considered to be thepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is aimed,therefore, in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An electrographic recording system for recording on a record mediumhaving a charge retentive surface, said system comprising:

a plurality of arrays of recording electrodes, with each recordingelectrode mounted with an area thereof in close proximity to said chargeretentive surface;

circuit means interconnecting like-numbered recording electrodes ofseparated arrays to establish at least two electrically independentgroups of arrays, with each array of each group separated from everyother array of said group by at least one array of another group;

a plurality of complementary electrodes mounted with an area of each inelectrical cooperative relationship with said record medium, eachcomplementary electrode being mounted adjacent to a single array of agroup of arrays and spaced from all other arrays of said group by atleast a portion of an array of another group;

means for applying a first voltage of one polarity to any selectedrecording electrode; and

means for applying a second voltage of opposite polarity to at least onecomplementary electrode adjacent to the selected recording electrode, incoincidence with said first voltage.

2. A recording system as described in claim 1 wherein the record mediumis threaded between the recording electrodes and the complementaryelectrodes and is in intimate contact with the complementary electrodes.

3. A recording system as described in claim 2 wherein the second voltageis applied to all complementary electrodes which are closer to the arraycontaining the selected recording electrode than they are to any otherarray in the group of arrays containing the selected electrode.

4. A recording system as described in claim 1 wherein the record mediumhas a conductive portion which is not held at ground potential, and thecomplementary electrodes are mounted in electrical contact with theconductive portion of the record medium.

5. A recording system as described in claim 4 wherein the second voltageis applied to all complementary electrodes which are closer to the arraycontaining the selected recording electrode than they are to any otherarray in the group of arrays containing the selected electrode.

6. A recording system as described in claim 1 wherein the record mediumhas a conductive portion which is not held at ground potential, and thecomplementary electrodes are mounted adjacent to the charge retentivesurface of the record medium and thereby are capacitively coupled to theconductive portion of the record medium.

7. A recording system as described in claim 6 wherein the second voltageis a voltage pulse.

8. A recording system as described in claim 7 wherein the coincidentvoltage pulse is applied to all complementary electrodes which arecloser to the array containing the selected recording electrode thanthey are to any other array in the group of arrays containing theselected electrode.

9. A recording system as described in claim 7 wherein the complementaryelectrodes are arranged in pairs, the two electrodes of each pair beingelectrically connected together and disposed on opposite sides of thesaid adjacent array of recording electrodes.

'10. A recording system as described in claim 7 wherein the arrays ofrecording electrodes are disposed in a line across the record medium andcomplementary electrodes are disposed in a line parallel to the line ofarrays.

11. An electrographic recording system for recording on a record mediumhaving a conductive layer and a charge retentive dielectric layer withan exposed surface comprising:

a plurality of recording electrodes, each mounted with an area thereofin close proximity to said surface, the recording electrodes beingdisposed in a row across the record medium and being divided into equalarrays;

circuit means interconnecting like-numbered recording electrodes of allodd-numbered arrays, and circuit means interconnecting like-numberedrecording electrodes of all even-numbered arrays;

2 (N+l) complementary electrodes, each having length slightly less thanthe length of one array, mounted in close proximity to said surface,thereby being capacitively coupled to said conductive layer, one-half ofsaid complementary electrodes being disposed in a row parallel to therow of recording electrodes on one side thereof and adjacent theretowith the end complementary electrodes extending beyond the row ofrecording electrodes, the other half of said complementary electrodesbeing similarly disposed on the other side of the row of recordingelectrodes;

means for applying a first voltage of one polarity to any selectedrecording electrode; and

means for applying a voltage pulse of opposite polarity to the fourcomplementary electrodes which are adjacent to the array containing theselected recording electrode, in coincidence with said first voltage.

Notice of Adverse Decision in Interference In Interference No; 98,422involving Patent No. 3,653,065, A. D. Brown, J12, ELECTROGRAPHICRECORDING SYSTEM WITH INTER- LEAVED ELECTRODE GROUPS, final judgmentadverse to the patentee was rendered Nov. 25, 1975, as to claims 2, 3, 4and 5.

[Ofiicz'al Gazette June 22, 1.976.]

Disclaimer 3,653,065.A"Zing Dim Bwown, J7"., Cleveland Heights, Ohio.ELECTRO- GRAPHIC RECORDING SYSTEM WITH INTERLEAVED ELECTRODE GROUPS.Patent dated Mar. 28, 1972. Disclaimer filed May 26, 1976, by theassignee, Gould Inc. Hereby enters this disclaimer to claims 2, 3, 4 and5 of said patent.

[Oflicz'al Gazette August 10, 1,976.]

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,653,065 Dated March 28, 1972 Inventor(s) Arling Dix Brown, Jr.

It is certified that error appears in the aboveidentified patent andthat said Letters Patent are hereby corrected as shown below:

Column 3, line 3h, "1.25 mil Should read O.25 mil-.

Column 7, line 12, "fourth" should read "fourth, Column 9, line L B,"50th pulse should read 50th clock pulse.

Column ll, line 21, "into: equal arrays" should read --into N equalarrays-.

Signed and Scaled this ninth Day Of March 1976 [SEAL] Attest.

RUTH C. MASON C. MARSHALL DANN Atresting Offi'cer Commissionernj'Patents and Trademarks

1. An electrographic recording system for recording on a record mediumhaving a charge retentive surface, said system comprising: a pluralityof arrays of recording electrodes, with each recording electrode mountedwith an area thereof iN close proximity to said charge retentivesurface; circuit means interconnecting like-numbered recordingelectrodes of separated arrays to establish at least two electricallyindependent groups of arrays, with each array of each group separatedfrom every other array of said group by at least one array of anothergroup; a plurality of complementary electrodes mounted with an area ofeach in electrical cooperative relationship with said record medium,each complementary electrode being mounted adjacent to a single array ofa group of arrays and spaced from all other arrays of said group by atleast a portion of an array of another group; means for applying a firstvoltage of one polarity to any selected recording electrode; and meansfor applying a second voltage of opposite polarity to at least onecomplementary electrode adjacent to the selected recording electrode, incoincidence with said first voltage.
 2. A recording system as describedin claim 1 wherein the record medium is threaded between the recordingelectrodes and the complementary electrodes and is in intimate contactwith the complementary electrodes.
 3. A recording system as described inclaim 2 wherein the second voltage is applied to all complementaryelectrodes which are closer to the array containing the selectedrecording electrode than they are to any other array in the group ofarrays containing the selected electrode.
 4. A recording system asdescribed in claim 1 wherein the record medium has a conductive portionwhich is not held at ground potential, and the complementary electrodesare mounted in electrical contact with the conductive portion of therecord medium.
 5. A recording system as described in claim 4 wherein thesecond voltage is applied to all complementary electrodes which arecloser to the array containing the selected recording electrode thanthey are to any other array in the group of arrays containing theselected electrode.
 6. A recording system as described in claim 1wherein the record medium has a conductive portion which is not held atground potential, and the complementary electrodes are mounted adjacentto the charge retentive surface of the record medium and thereby arecapacitively coupled to the conductive portion of the record medium. 7.A recording system as described in claim 6 wherein the second voltage isa voltage pulse.
 8. A recording system as described in claim 7 whereinthe coincident voltage pulse is applied to all complementary electrodeswhich are closer to the array containing the selected recordingelectrode than they are to any other array in the group of arrayscontaining the selected electrode.
 9. A recording system as described inclaim 7 wherein the complementary electrodes are arranged in pairs, thetwo electrodes of each pair being electrically connected together anddisposed on opposite sides of the said adjacent array of recordingelectrodes.
 10. A recording system as described in claim 7 wherein thearrays of recording electrodes are disposed in a line across the recordmedium and complementary electrodes are disposed in a line parallel tothe line of arrays.
 11. An electrographic recording system for recordingon a record medium having a conductive layer and a charge retentivedielectric layer with an exposed surface comprising: a plurality ofrecording electrodes, each mounted with an area thereof in closeproximity to said surface, the recording electrodes being disposed in arow across the record medium and being divided into equal arrays;circuit means interconnecting like-numbered recording electrodes of allodd-numbered arrays, and circuit means interconnecting like-numberedrecording electrodes of all even-numbered arrays; 2 (N +1) complementaryelectrodes, each having length slightly less than the length of onearray, mounted in close proximity to said surface, thereby beingcapacitively coupled to said conductive layer, one-half of saidcomplementary electrOdes being disposed in a row parallel to the row ofrecording electrodes on one side thereof and adjacent thereto with theend complementary electrodes extending beyond the row of recordingelectrodes, the other half of said complementary electrodes beingsimilarly disposed on the other side of the row of recording electrodes;means for applying a first voltage of one polarity to any selectedrecording electrode; and means for applying a voltage pulse of oppositepolarity to the four complementary electrodes which are adjacent to thearray containing the selected recording electrode, in coincidence withsaid first voltage.